Python class
Define a class
Method * * init()**
Python automatically runs this method whenever a new instance is created. In this method name, there are two underscores at the beginning and the end, which is a convention to avoid name conflicts between Python default methods and ordinary methods.
class Dog(): """Dog like class""" def __init__(self,name,age): """Initialize properties""" self.name=name self.age=age def sit(self): """Dog squatting""" print(self.name.title()+" is now sitting.") def roll(self): """Dog rolling""" print(self.name.title()+" is now rolling")
Calls to properties and methods
dog=Dog("bobby",4) print("The dog's name is "+dog.name.title()+",age is "+str(dog.age)+".") dog.sit() dog.roll()
Program output:
The dog's name is Bobby,age is 4. Bobby is now sitting. Bobbyis now rolling
Modify the value of the property
There are three different ways to modify the value of an attribute: modifying directly through an instance, setting by a method, and increasing by a method.
1. Modify directly by instance
class Animal(): def __init__(self,name,age): self.name=name self.age=age self.home='china' def get_info(self): info=self.name+" "+str(self.age)+" "+self.home return info bird=Animal('lucy',3) print(bird.get_info()) bird.age=bird.age+1 print(bird.get_info())
Program output:
lucy 3 china lucy 4 china
2. Modify attribute value by method
class Animal(): def __init__(self,name,age): self.name=name self.age=age self.home='china' def set_name(self,name): self.name=name def get_info(self): info=self.name+" "+str(self.age)+" "+self.home return info bird=Animal('lucy',3) print(bird.get_info()) bird.set_name('qiu') bird.set_age(6) print(bird.get_info())
Program output:
lucy 3 china qiu 6 china
3. Increase the value of attribute by method
class Animal(): def __init__(self,name,age): self.name=name self.age=age self.home='china' def update_age(self): self.age+=1 def get_info(self): info=self.name+" "+str(self.age)+" "+self.home return info bird=Animal('lucy',3) print(bird.get_info()) bird.update_age() bird.update_age() print(bird.get_info())
Program output:
lucy 3 china lucy 5 china
inherit
When a class inherits another class, it will automatically obtain all the properties and methods of the other class; the original class is called the parent class, and the new class is called the child class. The child class inherits all the properties and methods of the parent class, and can also define its own properties and methods.
When you create a subclass, the subclass must be included in the current file and preceded by the subclass.
When defining a subclass, you must specify the name of the parent class in parentheses.
class Animal(): """Create an animal class""" def __init__(self,name,age): self.name=name self.age=age def set_name(self,name): self.name=name def set_age(self,age): self.age=age def eat(self): print(self.name.title()+" can eat") def sleep(self): print(self.name.title()+"can sleep") def get_info(self): info=self.name+" "+str(self.age) return info class Cat(Animal): """establish Cat inherit Animal""" def __init__(self,name,age): super().__init__(name,age) self.home='China' def get_info(self): info=self.name+" "+str(self.age)+" "+self.home return info cat=Cat("kitty",2) print(cat.get_info()) cat.eat() cat.sleep()
Program output:
kitty 2 China Kitty can eat Kittycan sleep
Start by making the code structure as simple as possible. First, complete all the work in one file as much as possible, make sure everything can work normally, and then move the class to a separate module.
Class coding style
1. The hump naming method shall be adopted for the class name, that is, each word in the class name shall be capitalized without underline.
2. Instance name and module name are in lowercase format and underlined between words.
3. For each class, include a document string immediately after the class definition. Each module should also contain a document string that describes what classes can be used for.
4. You can use blank lines to organize your code, but don't abuse them. In a class, you can use an empty row to separate methods; in a module, you can use two empty rows to separate classes.
5. If you need to import the modules in the standard library and the functions you write at the same time, first write the import statement of the standard library module, then add a blank line, and then write the import statement of the module you write yourself.